JPH0114679B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a flexible tube-shaped heater, which is suitable for use as, for example, various catheter tubes having a medical heating function, piping tubes having a heating function in various fluid control devices, and the like. For example, when a medical liquid such as blood, artificial blood, Ringer's solution, or dialysate is introduced into a tube-shaped heater and heated, the tube is chemically inert to the introduced liquid, at least on its inner surface.
In addition, the tube must be free of toxic substances and exudates (that is, harmless), must have an even heating effect on each length of the tube, and must have internal and external insulation throughout. be. For example, in gas chromatography analysis of exhaled breath, in order to collect moisture in exhaled breath without condensation, a tube-shaped heater is inserted into the lungs to collect exhaled air. When used by inserting the tube into the organ, in addition to the above conditions, the tube's outer surface must also be made of harmless material, be easy to insert into the organ, and do not damage the tissue surface of the organ during the insertion process. As such, it is necessary that the tube has good overall flexibility and kink resistance, that the outer surface is soft and smooth, and that internally circulating gas does not leak through the tube wall. Conventionally, tube-shaped heaters generally used for the above-mentioned purposes are made by embedding nichrome wire back and forth within the thickness of a resin tube made of an appropriate material, but when the tube is cut to an appropriate length, the tube It is necessary to connect the ends of the reciprocating nichrome wire, which have been cut off, to each other in order to form a closed circuit. However, it is difficult to completely connect nichrome wires, and incomplete connections may cause electrical leakage. Electrical leakage must be strictly prevented in the case of medical supplies. Further, a voltage drop occurs between the input end and the tip of the nichrome wire, so a high applied voltage is required, but in the case of medical products, high applied voltage is not desirable for safety reasons. Additionally, the rigidity of the nichrome wire poses a problem in the flexibility of the tube as a whole. The present invention has various performances required for a medical catheter tube having a heating function, for example, and can be manufactured economically without the drawbacks of the conventional nichrome wire. The purpose is to provide a tube-shaped heater, which includes an inner layer of the tube made of fluororesin, a heating layer made of a tape-shaped heating element wound spirally around the outer circumferential surface of the inner layer of the tube, and a heating layer that covers the outer periphery of these layers. and a tube outer layer made of fluororesin, and the tape-shaped heating element has at least two conductors arranged longitudinally in contact with the conductive fluororesin tape in parallel and spaced relationship, and these conductors are made of fluororesin. The gist of the present invention is a flexible tube-shaped heater which is integrally covered with a protective layer, and at least one of the tube inner layer and the tube outer layer is made of a continuous porous stretched polytetrafluoroethylene resin. Tetrafluoroethylene resin PTFE, copolymer of tetrafluoroethylene and hexafluoropropylene FEP, copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether PFA, copolymer of tetrafluoroethylene and ethylene ETFE, etc. Compared to other types of resins, fluororesins generally dissolve, decompose, and dissolve naturally or with chemicals.
It is chemically extremely stable and does not easily dissociate or change, has no or almost no toxicity or harmful effects on living organisms, is safe, has excellent antithrombotic properties (anticoagulant properties), is water repellent, slippery, and heat resistant. It is a substance that has properties such as excellent electrical properties and high electrical insulation resistance.
Above all, PTFE is excellent in the above properties. In addition to the above-mentioned excellent properties of PTFE, the continuous pore stretched porous material of PTFE (hereinafter referred to as E-PTFE) has an extremely high level of continuous pore porous fleshy structure formed by the stretching process. It has excellent flexibility and high tensile strength due to advanced molecular orientation. The present invention relates to the above-mentioned fluororesin and E-
Focusing on PTFE, as mentioned above, the tube inner layer, heat generating layer, and outer layer are all made of fluororesin, and at least one of the tube inner layer and tube outer layer, that is, the inner layer, the outer layer, or both, is made of E-
It is made of PTFE, and its basic composition is:
As shown in FIG. 1, it consists of a tube inner layer 1, a heat generating layer 2 consisting of a tape-shaped heating element 21 wound spirally around the outer circumferential surface of the tube inner layer 1, and a tube outer layer 3 covering these outer circumferential surfaces. ing. (a) Tube inner layer 1 of fluororesin If it is made of solid internal material, for example,
Fluororesins other than PTFE can be melt-extruded, so they can be manufactured by melt-extruding them into a tube shape. In the case of PTFE, a PTFE-filled tube can be produced by forming a paste-like mixture of the powder and an extrusion aid into a tube and then firing it. Also, fluorine resin (including PTFE)
It can be produced by winding a thick tape-like material or a sheet-like material around a heat-resistant core rod in a spiral or glue-like manner and heat-treating the material. In addition, if E-PTFE (i.e., a continuous porous fleshy structure of tetrafluoroethylene resin) is used, for example, the method disclosed in Japanese Patent Publication No. 18991/1983, that is, PTFE powder and extrusion aid. A paste-like mixture is extruded into a tube shape, the extruded tube is then stretched, and then the stretched tube is fired in a state where heat shrinkage is prevented. As a result, it is possible to produce a stretched porous material with fine continuous pores composed of fine nodules and fine fibrils. Also, fired or semi-fired E-
It can also be produced by winding a PTFE tape or sheet material around a heat-resistant core rod in a spiral or glue-like manner and heat-treating it. (b) Heat generating layer 2 The heat generating layer 2 provided on the outer surface of the tube inner layer 1 has a tape-shaped heat generating element 21 as shown in FIG.
The tube inner layer 1 is formed by winding the tube helically around the outer surface of the tube inner layer 1 along its length. The tape-shaped heating element 21 used in this example is as shown in FIG. Two narrow and thin fluororesin tapes 24, 2 are covered with tape-shaped metal foil conductors 23, 23 and serve as protective layers.
It is made by sandwiching and wrapping it between four pieces of sandwich paper and then heat-sealing or gluing the whole thing together. The conductive fluororesin tape 22 is made by mixing a suitable fluororesin with conductive powder such as graphite powder, carbon black powder, carbon fiber, metal powder, etc. in an appropriate ratio to give it appropriate conductivity (for example, , PTFE
Conductive carbon black in fine powder
10wt% coagulate method, blended with about 40wt% naphtha as an auxiliary agent, extruded the blend using a ram extruder, rolled down to a thickness of 4 mil, and removed the naphtha by evaporation). When a voltage is applied between the parallel conductors 23, 23, the conductive fluororesin tape 2 between the conductors 23, 23
Current flows in each part of the tape 22 in the width direction of the tape 22, and each part of the tape 22 generates heat over its entire length. The conductors 23, 23 are conductive fluororesin tape 22
It may be provided in the form of being embedded within the wall thickness. Also, in order to obtain more effective heat generation, conductors 23, 23
As in the flat heating electric wire according to the applicant's previous proposal (Utility Application No. 1983-9524), three or more conductors are provided in a parallel and spaced relationship, and the plurality of conductors are selectively connected to each other. It is preferable to apply a voltage or to alternately apply opposite potentials between the conductors. In addition to having the conductive fluororesin tape 22 exist over the entire length in the longitudinal direction, it can also be placed intermittently at appropriate intervals, and by doing so, the tube can be divided into areas that generate heat and areas that do not. can be provided. (c) Tube outer layer 3 made of fluororesin If it is to be made of solid flesh, PTFE is added to the outer peripheral surface of the tube inner layer 1 on which the heat generating layer 2 is formed.
It is formed by applying other fluororesin (PFA, etc.) by melt extrusion coating method. In the case of PTFE, it is applied by a paste extrusion coating method and then fired.
It can also be formed by winding a thick-walled tape or sheet material of fluororesin (including PTFE) into a spiral or pastel shape and heat-treating it. If it is made of E-PTFE, it can be formed by heating a fired or semi-fired E-PTFE tape or sheet by winding it in a spiral or spiral shape. can. According to the tube-shaped heater of the present invention, the following effects can be obtained. (1) Since fluororesin is used as the material for the inner and outer layers 1 and 3 of the tube, both the inner and outer surfaces of the tube are chemically inert and free of toxicity and exudates. (2) The heat generating layer 2 is made of a conductive fluororesin tape 22 and two or more conductors in a parallel and spaced relationship that are in contact with the tape 22 or are embedded in the tape and are vertically aligned along the length of the tape. 23, 23
Since the tape-shaped heating element 21 is integrally coated with a protective layer consisting of two fluororesin tapes 24, 24, even if the tube is cut, the conductors 23, 23 at the cut ends can be connected to each other as described above. Unlike tubes using nichrome wires, there is no need for connection processing, and at least the exposed conductor end surface of the cut end of the tube is insulated with insulating tape such as unfired PTFE tape, or coated with insulating resin liquid. It is sufficient to apply insulation coating. In this case, even if a conductive liquid enters between the tube inner layer 1 and the tube outer layer 3, the conductor 23,
Since the tube 23 is not exposed, there is no possibility of short-circuiting, and therefore, it is not necessary to completely prevent liquid from entering over the entire circumference of the cut end surface of the tube, making the terminal treatment easy. Furthermore, the fact that both the inner and outer layers 1 and 3 of the tube and the heat generating layer 2 are made of fluororesin having excellent electrical insulation properties also makes the whole tube electrically safe (no leakage occurs). Also, unlike a tube using nichrome wire, the applied voltage acting on the conductive fluororesin tape 22 is the same throughout the length of the tape 22, so the input voltage can be lowered, and Each part of the tube generates heat equally, that is, the tube generates heat evenly over its entire length. (3) The heat generating layer 2 is not a nichrome wire but a conductive fluororesin tape, and the inner layer 1 or outer layer 3 of the tube, or both 1 and 3, are made of open-cell stretched porous polytetrafluoroethylene resin. Material (E-
By using PTFE), the overall bending flexibility is significantly improved and the kink resistance is improved compared to the case where the heat generating layer is made of nichrome wire or the inner and outer layers of the tube are made of solid material. Furthermore, E-PTFE has improved mechanical properties such as tensile strength or has excellent durability through stretching. In addition, the inside and outside insulation properties are also excellent. In this case, E-PTFE (fibril length approximately 1 to 1000 μm) has a porous structure with continuous pores, but liquid is difficult to penetrate due to the excellent water repellency of PTFE. However, if gas permeation becomes a problem, a sealing layer may be formed by applying, for example, a fluorine rubber liquid to the outer circumferential surface of the E-PTFE tube inner layer 1 or the outer circumferential surface of the outer layer 3 and drying it. Just do it like this. (4) The inner and outer surfaces of the tube are extremely slippery due to the excellent lubricity of fluororesin. In addition, when a tube heater is constructed by using E-PTFE for both the inner and outer layers 1 and 3 of the tube, both the inner and outer surfaces of the tube are soft, and when the tube is bent, wrinkles do not form on the inner surface of the bent portion. Does not occur. Therefore, the flow of the fluid introduced into the tube is extremely good, and in conjunction with the good flexibility mentioned in (3) above, the insertion into the organ is extremely smooth, and the organ tissue surface is not touched during the insertion process. It can be done without causing any damage. (5) Due to the excellent heat resistance and chemical resistance of fluororesin, sufficient disinfection by high temperatures and strong chemicals is possible, and there is a great degree of freedom in selecting the disinfection or cleaning method. (6) If at least the tube inner layer 1 is made of E-PTFE, the tube-shaped heater can also be used as an antithrombotic artificial blood vessel with a heat-retaining or heating effect. Therefore, it has excellent heat resistance and chemical resistance, and is capable of heating liquids up to about 200°C and heating corrosive liquids, including tubes for constructing various catheters and artificial blood vessels that have the aforementioned medical heating function. Therefore, it is effective and suitable as a fluid heating tube or piping tube having a heating function in various fluid control devices. Example 1 A PFA melt-extruded tube with an inner diameter of 2.0 mm and an outer diameter of 2.6 mm was used as the inner layer 1 of the tube, and a tape-shaped fluororesin heating element 21 having the configuration as shown in FIG. 2 was attached to the outer peripheral surface of the tube.
(width 5mm, thickness 0.3mm, inner distance between conductors 23, 23
1.9mm, electrical resistance 30Ω per meter) pitch 10mm
The heat generating layer 2 was then spirally wound as shown in the example in FIG. Next, three layers of unfired 3-fold stretched porous PTFE tape (unfired E-PTFE tape) with a thickness of 0.1 mm were wrapped around the outer peripheral surface of the tube on which the heat generating layer 2 was formed, and the tube was placed in a molten salt bath at 370°C. The tube-shaped heater of the present invention was obtained by immersing the tube in water for 10 seconds and firing it, and then cooling it in water to form the tube outer layer 3. This tube-shaped heater had an outer diameter of 4.0 mm, was highly flexible, and had a soft and slippery outer surface, making it suitable as a catheter tube to be inserted into the esophagus, lungs, and other organs. When a voltage of 7V was applied between the conductors 23 and 23 terminals at one end of the tubular heater cut into a length of 2 m, the temperature inside the tube was 37°C (room temperature 26°C),
The temperature reached 42℃ when 10V was applied. Also, in the above case, when air was introduced into each tube at a flow rate of 0.1 m, each
Warmed air at 35°C and 28°C was obtained. Example 2 In Example 1, as the tube inner layer 1, the inner diameter
2.0mm, 1.5x stretched porous fired PTFE with outer diameter of 2.6mm
0.1 on the outer circumferential surface of the tube (E-PTFE tube)
The heat generating layer 2 was prepared in the same manner as in Example 1 except that a fluororesin liquid was applied to a thickness of mm and sealed.
The outer layer 3 was sequentially formed to obtain a tube-shaped heater of the present invention. In addition, in order to prevent the inner layer 1 from being crushed when forming the heat generating layer 2 and the outer layer 3, and to facilitate the formation of the layers 2 and 3, a copper wire with a diameter of 1.9 mm was inserted as a shape-retaining mandrel into the inner layer 1. After the heater was completed, the copper wire was pulled out and removed. This tube-shaped heater is highly flexible, has an antithrombotic inner surface, and a soft and slippery outer surface, making it ideal for heating blood. It is also suitable as a catheter tube for organ insertion. When a voltage of 15V was applied between the conductors 23 and 23 terminals at one end of the tubular heater cut into a length of 2 m, the temperature inside the tube became 55°C (room temperature 26°C), and water (21°C) was heated at a flow rate of 0.1 m. ) was poured and the temperature was 36℃.
of heated water was obtained. In addition, the temperature of the tube can be appropriately controlled by incorporating or contacting a temperature sensor such as a thermoelectric body in the heating element part of the tube or at an appropriate location, and connecting this to a temperature control device.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of a flexible tube-shaped heater according to the present invention, and FIG. 2 is a partially cutaway enlarged perspective view of a tape-shaped heating element used therein. 1: tube inner layer, 2: heat generating layer, 3: tube outer layer, 21: tape-shaped heating element, 22: conductive fluororesin tape, 23: conductor.

Claims (1)

[Claims] 1. A tube inner layer made of a fluororesin, a heat generating layer made of a tape-shaped heating element wound spirally around the outer peripheral surface of the tube inner layer, and a tube outer layer made of a fluororesin covering the outer periphery thereof,
The tape-shaped heating element is made by arranging at least two conductors in contact with a conductive fluororesin tape in a parallel and spaced relation to each other in the longitudinal direction, and covering them integrally with a protective layer made of fluororesin. , a flexible tube-shaped heater in which at least one of the tube inner layer and the tube outer layer is made of a continuous porous stretched polytetrafluoroethylene resin material;